capital allowance WDA

hi, i am not sure where this £5000 comes from , please someone help,why bmw not use WDA 20% MANY THANK
THIS IS ON OSBORNE BOOK BUSINESS TAX P6.15
partnership business
single asset pool for car (BMW) WITH 25% private use by jo £!5,000
during accounting period, 12 months to 31/3/2010 following asset were acquired and disposed of
on 30/12/2009 a used audi car was bought for £25,000, 25% private use,emission level is 150g/km
on 30/12/2009 the BMW was sold for £14,000